Update to Python3

[AndrewFasano]

After updating the core panda scripts to all be python3, things have broken with the jenkins test. Looks like we kick things off with python ptest.py which on the jenkins box is python2.

Unfortunately just running python3 ptest.py doesn't seem to work. Might be an easy fix if we can just run 2to3 on it. I'm not sure how to update the infrastructure though.

@tnballo are you the one maintaining this these days? Any chance you'd have cycles to investigate next week?

[tnballo]

@AndrewFasano Will take a look! Haven't thought about the test repo in a while, will also open up issues for other test-infrastructure-related tasks so I don't lose track of them.

[tnballo]

Progress update on this issue (all in panda-re/panda, not this repo):

• Updated panda/scripts/install_ubuntu.sh to keep in sync with the python3 docker build (Jenkins currently uses the former, which we probably want to keep that way to ensure non-Docker build is working).
• Updated panda_jenkins.sh (script only the the CI server ATM) to use python3 where appropriate, removed re-do of tests already in GitHub actions (e.g. QEMU build, taint).
• Updated panda/testing/*.py with 2to3.

This fixed some CI issues, but not all of them. The root cause for the current CI failure is panda/testing/ptest.py not working as expected after the update to python3 - does not throw an error but a test that should pass is failing (asidstory replay). Will take a closer look at that next.